LOS ANGELES, Feb 28 - Leonardo DiCaprio won his first Oscar on Sunday for his leading role in revenge movie "The Revenant," as "Spotlight" won the prize for best picture.

DiCaprio, 41, had been nominated four times previously for an Oscar over a career spanning 25 years.

But he was favorite to finally take home the best actor Academy Award this year for his grueling portrayal of a fur trapper left for dead in an icy wilderness after being mauled by a bear.

In a fight for survival, his "Revenant" character Hugh Glass treks through snow-covered forests, gets swept away in a waterfall, sleeps inside the carcass of a disemboweled horse and hungrily eats raw bison liver before making it back to his camp.

DiCaprio, a bachelor with a string of supermodel girlfriends, has matured into one of the world's most admired and popular actors, as well as a champion of environmental causes ranging from marine reserves to the rights of indigenous people.

In his acceptance speech, DiCaprio, who received a standing ovation, said: "Let us not take this planet for granted. I do not take tonight for granted."

DiCaprio added: "Our production needed to move to the southern tip of this planet to find snow. Climate change is real, it is happening now. It is the most urgent threat facing our entire species and we need to work collectively together, and we need to support leaders around the world who do not speak for the big polluters and the big corporations but who speak for all of humanity."

DiCaprio had already won Golden Globe and Screen Actors Guild trophies for the role, which transformed the heartthrob from movies like "Titanic" and "Romeo + Juliet" into a greasy-haired 1820s fur trapper who barely speaks after the bear ripped his throat.

DiCaprio won his first Oscar nomination in 1994 for his supporting role as a mentally challenged boy in "What's Eating Gilbert Grape."

His romantic "Romeo + Juliet" and "Titanic" roles went unrecognized by the Academy of Motion Picture Arts and Sciences, and it was another 10 years before his obsessive-compulsive Howard Hughes in "The Aviator" brought a second Oscar nomination.

Nominations for 2006's "Blood Diamond" and 2013's "The Wolf of Wall Street" came and went without DiCaprio taking home the most coveted trophy in show business. 

Mexico's Alejandro Iñárritu also won the best director Oscar for "The Revenant".

Iñárritu was the first filmmaker in 60 years to win a back- to-back director's Oscar. Iñárritu won best director last year for "Birdman," which also won the 2015 best picture Academy Award.

It was the fourth Oscar for Iñárritu and came as little surprise after he won a Golden Globe, a British BAFTA award and a trophy from the Directors Guild Awards for the film.

The movie also won best original screenplay.

Producers Steve Golin, Blye Pagon Faust, Nicole Rocklin and Michael Sugar (L-R) of the Best Picture winning film "Spotlight", kiss their Oscars backstage during the 88th Academy Awards in Hollywood, California February 28, 2016. Photo: Reuters

"This film gave a voice to survivors, and this Oscar amplifies that voice, which we hope can become a choir that will resonate all the way to the Vatican," said producer Michael Sugar.

Rising star Brie Larson, 26, took home the statuette for best actress for her role as an abducted young woman in indie movie "Room," adding to her armful of trophies from other award shows.

Brie Larson won her first Oscar for best actress on Sunday for her moving portrayal of a young woman held captive for years with a son in the emotional thriller "Room."

Larson, 26, won praise for her role as 'Ma' in the film in which she plays an abducted woman patiently seeking ways to escape from a small, dark and oppressive room.

"The thing I love about movie making is how many people it takes to make it," Larson said, thanking everyone involved in making and supporting the film.

"Thank you to the movie-goers for going to the theaters and seeing our films," she added.

The actress was the front-runner for the honor after winning Golden Globe, BAFTA, Spirit and Screen Actors Guild awards.

It was the first Oscar nomination for Larson, who has starred in more than 45 films and television shows since beginning her career as a child actress almost 20 years ago.

Previous roles, often as a supporting actress, spanned comedy and drama such as "21 Jump Street" and "The Spectacular Now."

The Hungarian movie "Son of Saul," a harrowing Holocaust drama, won the Oscar for best foreign language film.

It was Hungarian-French director László Nemes' first full-length film, which had been seen as the favorite to win the award after it won a Golden Globe for best foreign language film and took the second-highest prize at the Cannes Film Festival.